Many integrated circuits include circuitry that may use resistors and capacitors as parts of their passive elements used to perform their associated functionalities. For example, various basic analog circuits such as amplifiers, filters, oscillators, and power supplies, and many of the more complex circuitries such as receivers, transmitters, analog-to-digital convertors, etc. may include capacitor and resistor elements. On-chip resistor elements may be implemented, for example, in bipolar technology, by resistor structures such as based-diffused, emitter-diffused, ion implanted, and epitaxial resistors or by thin-film poly-silicon resistors (poly-resistors). The resistance value of an on-chip resistor may be expressed in terms of dimensions such as length (L), width (W), and the sheet resistivity (Rsq). The sheet resistivity may depend on a number of parameters such as the material of the structure and the process used, and may vary with temperature and from process-run to process-run and even from wafer to wafer.
On-chip capacitor structures may include MOS and junction capacitors. For example, in bipolar technology, an on-chip capacitor may be implemented by forming a metal layer (e.g., aluminum) on a thin oxide layer (e.g., SiO2 layer) grown, for instance, on an emitter diffusion. On-chip resistor and capacitor values may be calibrated using on-chip calibration circuits and off-chip reference elements such as accurate resistors and capacitors. The use of the off-chip elements specifically for calibration purposes may use one or more pins of the chip as dedicated for connecting the off-chip elements.